Patent GB-706082-A (GB)
Title: Improvements in or relating to x-ray machine and diaphragm assembly therefor
Inventor: BILLIN ARTHUR GILBERT
IPC: G21K1/02
Filed: 1952-05-21
Abstract: 706,082. X-ray apparatus. LIEBEL-FLARSHEIM CO. May 21, 1952, No. 12836/52. Class 98(1) A diaphragm assembly comprises a diaphragm such as a Bucky grid slidably supported in a frame for linear movement in opposite directions, a reversible motor mounted on the frame, a drive pulley, a string or like member connecting the drive pulley with the diaphragm for moving it in both directions as determined by the direction of movement of the motor, and control means responsive to the movement of the diaphragm for reversing the motor at predetermined points in the movement of the diaphragm. As shown, the Bucky diaphragm 1 is mounted to slide in a frame 8. One edge of the diaphragm has guide blocks 6, 7 slidable on rods 11' supported by brackets 12 on a partition wall 10 of the frame 8. The actuating and control elements are housed in the space 9 between wall 10 and the side of frame 8. A string or like member 20, which may be of nylon fibre, is connected to plates 16, 17 on blocks 6. 7, and passes round, and may be connected to, a pulley 21 driven by a reversible electric motor through reduction gear. The gearing is such that the diaphragm is moved, when the motor is energized, at a speed such that grid shadows are avoided. The motor has a field winding and two shading coils. When both shading coils are opencircuited the motor is stationary, and when one coil is short-circuited the motor turns in one direction. To reverse the motor the first coil is open-circuited and the other short-circuited. This reversal can be performed a single-pole double-throw switch 44. Plate 17 cairies a plate 64 having dependent fingers 68, 69. At one extreme of the'travel of diaphragm 1 finger 69 engages a lever 60 to operate the switch; at the other extreme finger 68 engages a lever 59 which moves the switch back to its former position. Plate 16 has a projection which, when the diaphragm is moved as far as possible to the left, engages a roller 50 of a springy lever 48 which is pressed down to operate and open a "homing" switch 36. A second projection on plate 16 similarly operates an " exposure " switch 37 (not shown) mounted behind switch 36. The diaphragm actuating mechanism is connected by a plug-andsocket to X-ray apparatus, which includes a switch for initiating an exposure. When this switch is closed, a relay 72 (not shown), mounted in the space 9, is energized to short-circuit one of the shading coils through switch 44. As the diaphragm starts to move, the " homing " switch 37 is released and closes. A little later the " exposure " switch 36 closes to operate a contactor to energize the X-ray tube. Thus the tube is not energized until the diaphragm is in motion. At the end of its travel, the diaphragm operates switch 44, reversing the motor. At the end of its movement in the opposite direction, it operates switch 44 to reverse the motor again, and so continues a to-and-fro movement as long as the exposure-initiating switch is closed. The motor is so designed that the reversal of movement is sudden. When the exposure is complete the exposure-initiating switch is opened, by hand, by a timer, or by an exposure-integrating device. This de-energizes the X-ray tube contactor and the relay 72. The relay operates to disconnect switch 44 from the shading coils, but completes a circuit across one of the coils through the "homing" switch 37. This causes the diaphragm to move back to its initial position, passing the point of operation of switch 44, opening the " exposure " switch 36, and finally opening the " homing " switch 37, thus stopping the motor. The apparatus is then ready for another exposure.